1. Field of the Invention
The present invention relates to apparatus for use in detecting micro-organisms in samples of a substance and can be used, for example, for monitoring substances intended for human consumption, such as foods, drinks or pharmaceuticals, or may be used to monitor pathological samples, such as blood, in the laboratory.
2. Description of the Prior Art
Blood culturing techniques currently used in hospitals include a method in which a sample of blood is cultured in nutrient broth, from which samples are sub-cultured on agar plates at regular intervals. Not only is this method extremely slow with results not being expected for several days, but it is highly labour intensive and requires good aseptic conditions to be maintained throughout.
A quicker technique uses a machine sold under the trade name Bactec. To use this machine, the sample is exposed to a radioactive substrate which is consumed by the micro-organisms, which then give off radioactive carbon dioxide for detection by the machine. Although this machine gives results in hours, rather than days, hospital personnel may be worried by possible radioactive exposure and waste disposal.
Electrochemical methods have been proposed which include measuring conductance, impedance or potential difference changes, but known apparatus using these methods is not readily susceptible to hospital use in that the sample bottles are kept at a controlled temperature in a water bath which may become contaminated by spillage. In another known apparatus, instead of sample-holding bottles, special modules are required which are not suitable for filling directly from the hypodermic syringe used to remove blood from a patient, and an intermediate pipetting stage is necessary, with the result that time is wasted, labour is required and spillage, and hence contamination of personnel or equipment, is possible.
In our British Patent Specification No. 2,142,433B, we have described apparatus for use in detecting micro-organisms in any one of a plurality of samples, comprising a plurality of containers for the samples, each container having in its base at least one electrode contactable with the sample therein, and a container-mounting member having means for receiving and for locating each of said containers at a respective one of an array of stations, the container-mounting member comprising a base provided with electrical contact means at each station for electrical connection with the electrode of a container received at that station.